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Ohio Journal of Science (Ohio Academy of Science)
Ohio Journal of Science: Volume 5, Issue 6 (April, 1905)
1905-04
The Rate of Growth in Epistylis Flavicans
Landacre, F. L.
The Ohio Naturalist. v5 n6 (April, 1905), 327-329
http://hdl.handle.net/1811/1449
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April, 1905.]
Epistylis
flavicans.
327
THE RATE OF GROWTH IN EPISTYLIS FLAVICANS.
F. L. LANDACRE.
The writer recently had an opportunity to observe the rate
of growth in one of our common stalked • Protozoa., Epistylis
flavicans Ehr., and the changes in form of the animalcule which
accompany this growth.
A good deal of interest attaches to the rate of growth of the
pedicle in stalked forms on account of the fact that two species
frequently otherwise similar may be differentiated by the length
of pedicle. A form with branched pedicle, which in its adult
condition may be easily differentiated by the pedicle, is with difficulty separated from other species if its pedicle is still simple
as it is in the earlier stages of growth. Each form having a
branched stalk passes through a stage in which its stalk is simple
and it is then sometimes with difficulty separated from the forms
with unbranched pedicles.
The frequency with which these immature forms are met
with depends of course upon the time required for a detached
zooid to acquire a pedicle characteristic of the adult form. If
this is done uqickly, for instance, in a few hours, comparatively
few immature forms would be encountered. If the period of
growth is longer, for instance, several days or a week, one ought
to find immature forms rather frequently. During the three
summers spent in work on Protozoa at Sandusky no case of
growth except the present instance was observed that could be
measured. This may be due to the fact that work
was commenced about the first of June each year which wrould be after
the period of maximum growth among the Protozoa, this period
coming earlier in the spring.
In the present case the attachment of the free swimming
form was not observed. But in mounting a slide for observation
a large colony of Epistylis flavicans was found many of whose
zooids were detached and swimming about. Within a short time
one was found attached and its rate of growth observed. It
could have been attached only a short time for it still had the
typical cylindrical shape characteristic of free swimming forms
(Fig. 1). The posterior circle of cilia was vibrating rapidly and
there was only a faint movement of the cilia visible in the region
of the gullet.
In three minutes it had assumed the form of Fig. 2. The
posterior cilia were vibrating a little less rapidly. There was a
cone shaped extension at the posterior end of the body equalling
one-third of the total body length and extending proximally
from the posterior circlet of cilia. The body had begun to
assume the normal shape the adoral cilia were vibrating and the
328
The Ohio Naturalist.
[Vol. V, No 6,
total width of the peristome was about two-thirds of the adult
form. In two minutes more it had assumed the form shown in
Fig. 3, the posterior end had narrowed considerably and while
the constriction extending from the posterior ciliary wreath was
still one-third the total length of the body its attached end had
assumed the appearance of the adult pedicle. The lengthening
of this pedicle had every appearance of growth and not of metamorphosis of body into pedicle. The body while producing the
pedicle was actually larger than before, and although the form
was feeding rapidly it is hardly conceivable that assimilation and
growth could take place at the rate at which the pedicle appeared.
DESCRIPTION OF PLATE.
Fig. 1. Four stages in the growth of the pedicle of Ephistylis flavicaus
Ehr. p. c.—posterior circlet of cilia, p.—pedicle appearing first
in Fig. 3.
At the end of five minutes more (Fig. 4) the body of the
animalcule was nearly normal in every respect except that the
slight elevation on which the posterior circlet of cilia had been
situated could still be observed although the cilia had been
retracted. The pedicle at this time was one-sixth the length of
the body and the animalcule was feeding actively. From this
point on only the relative rate of growth in the pedicle will be
given as no opportunity offered to note any other histological
changes than those pertaining to the lenghtening of the pedicle.
At the end of five minutes more or a total of fifteen minutes
in all the pedicle was equal to one-fourth the length of the body;
in twenty minutes one-third; at twenty-five minutes one-half;
at thirty minutes, thirteen-twentieths; at thirty-five minutes,
four-fifths, and at the end of forty minutes equaled the body in
length.
It was not observed again for a period of forty-five minutes
during which time the pedicle had attained a length equal to
three times that of the body. This is somewhat under the normal, the unbranched pedicle usually being four to five times that
of the body. So that a period of one hour and a half was sufficient to produce a pedicle nearly equal to the unbranched por-
April, 1905.]
Meeting of the Biological Club.
tion of the adult colony stalk. Of course to make this observation complete the rate of division in the zooid should be observed
and also the rate of production of the branched portion of the
pedicle.
At the end of one hour and thirty-five minutes the posterior
circlet of cilia began to appear and in an hour and fifty-five
minutes the animalcule became detached and swam away.
The presence of the cover glass, the lack of oxygen and food
all three probably prevented the completion of the growth and
probably retarded the later stages of it but otherwise it seems
normal and furnishes some idea of the rate at which the single
stalked and branched stalked forms of Protozoa produce their
pedicles.
The rapid rate of growth also accounts for the rarity with
which one finds immature forms especially those with compound
pedicles and yet they do occur frequently enough to render the
difficulty of identifying these forms very great.
These observations were made in August and the rate of
growth may be quite different from that occurring earlier in the
summer during the period of greatest activity among the
Protozoa.
329